Siege of Gvozdansko

Croatian nobleman Nikola III Zrinski on a silver coin minted in Gvozdansko

In 1526, Ottoman forces led by Sultan Suleiman the Magnificent defeated a large Christian force at the Battle of Mohács. As King Louis II died in battle and had no heir, both the Kingdom of Hungary and the Kingdom of Croatia, which were in a personal union, became disputed territories between Ferdinand I, Archduke of Austria, from the House of Habsburg, and John Zápolya, Voivode of Transylvania. A civil war ensued, which enabled the Ottomans to gain more territory in Hungary. Most of the Croatian nobility backed the Habsburgs, expecting aid in the wars with the Ottoman Empire.[1]

Following the fall of the Banate of Jajce in 1527, the main line of Croatian defense moved to the valley of the Una River, where the Gvozdansko Castle was one of the main fortifications.[2] Gvozdansko was a square fort in possession of the Zrinski family, located on the main road between the towns of Dvor and Glina. It had four towers on its corners and a larger tower at the entrance. It was first mentioned in 1488 and was built to protect the nearby mines of iron, copper, lead, and silver.[3] The extraction of silver in Gvozdansko began in the late 15th and early 16th centuries, when the Zrinski family was led by count Nikola III Zrinski. The Zrinskis also minted their own silver coins in Gvozdansko.[2] The silver mines in their possessions yielded an annual income of 30,000 florins, according to reports from Nikola III,[4] who usually resided in Gvozdansko.[5] With growth of their wealth and influence, the family gained more land in the valley of the Una, such as the towns of Kostajnica, Krupa,[2] and Dubica, on the right bank of the Una. The Zrin Castle, which gave the name to the Zrinski family, was located northeast of Gvozdansko.[5]

In 1534, Nikola III died, and his wife Helen, and two sons, Nikola IV Zrinski (commonly known as Nikola Šubić Zrinski) and Ivan I, took the role of governing the family possessions.[6] In early 1537, Dubica was captured by Ghazi Husrev-beg, the sanjak-bey of Bosnia.[5] Shortly after the fall of Dubica, the Croatian nobility met in Zagreb to evaluate their defensive capabilities, and pointed out the lack of military forces and financial dificulties.[7] The Zrinskis started enrolling their miners as soldiers, and were able to take back Dubica in the same year. The Ottomans regained initiative in the war following the failure of Katzianer's Campaign in Ottoman-held Slavonia in October 1537. They recaptured Dubica in May 1538. Croatian forces again took control of Dubica in January 1540, which prompted a retaliatory attack led by Husrev-beg, Murat-beg Tardić, Sanjak-bey of Klis, and Mehmed-beg Jahjapašić from the Sanjak of Smederevo. The main targets were Kostajnica, which was briefly captured, and Zrin and Gvozdansko, which held off attacks.[8] Although a six-month peace treaty was in effect since 1 January 1540,[9] the Zrinskis were excluded from it.[10] The offensive, which began in early May, ended in mid June, on Husrev-beg's orders.[11] The Zrinskis reported that all of the mines near Gvozdansko were destroyed.[12] In late 1540, Ferdinand I approved more money to Nikola IV for military purposes. Two years later, Nikola was named Ban of Croatia.[10]

Ottoman raids in the Una valley continued in 1544 and 1546.[13] In June 1547, a five-year peace treaty was concluded between Ferdinand I and Suleiman. The treaty was respected on both sides.[14] Rüstem Pasha, Grand Vizier of the Ottoman Empire, unsuccessfully tried to get Nikola IV excluded from the treaty, due to his raids of Ottoman lands in earlier years.[15]

The Ottomans attempted to conquer the Gvozdansko Castle on several occasions.[16] The first major attempt was in 1566.[16] The second failed attempt was in 1561, when 8,000 Ottomans under the command of Malkoč-beg attacked the castle.[16] The third attempt was in 1574, when Ferhat-paša Sokolović tried to capture the castle by treachery.[16] Another attempt in 1576 by Kapidži-paša also failed.[16][17]

Map of Croatia and Ottoman expansion at the beginning of 1576

In early 1573, a large peasant revolt started in northwest Croatia. The rebellion was quickly suppressed, but with heavy casualties.[18] The revolt further worsened the financial and military situation in the country.[19] The Ottoman Empire concluded a peace treaty with the Republic of Venice in March 1573, which enabled local sanjakbeys to direct their forces towards Croatia. Throughout 1573 and 1574, several forts on the border were destroyed and Croatian forces were barely able to cope with the attacks. On 15 May 1574, the Croatian Parliament decided to build two new forts and strengthen seven, including Slunj, and introduce new levies to help raise funds. However, these measures did not have a significant effect on the overall state of the defense.[18]

On 19 December 1574, during a session of the Croatian Parliament, Gašpar Alapić was officially named co-Ban of Croatia, alongside Ban Juraj Drašković. Sultan Selim II died in the same month and was succeeded by his son Murad III.[20] Ferhad Pasha Sokolović led several offensives on border forts during 1575, including an unsuccessful attack on Bihać. In September, he defeated an army led by Habsburg General Herbard VIII von Auersperg, who was killed in battle, and then returned to the Sanjak of Bosnia. His actions during the year severely weakened the Croatian defense and enabled a breakthrough towards the Korana, Mrežnica, and Kupa rivers.[20]

Although Sultan Murad III confirmed his father's peace treaty with Emperor Maximilian II on 22 November 1575, Ottoman raids into the lands ruled by Maximilian II did not stop. There were 50-60 Ottoman incursions recorded in the following year.[21] In 1576, simultaneous attacks followed west of Una and between the Sava and Drava rivers.[20] In April 1576, around 7,000 Ottoman troops attacked the town of Hrastovica, north of Gvozdansko, but the town's garrison repelled the attack. In June, the Ottomans captured the town of Bužim, southwest of Gvozdansko, and soon started attacking the Gvozdansko Castle, whose garrison numbered 130 men. The Ottomans retreated after three days of fighting, when reinforcements led by Johann Auersperg, commander of the Croatian Military Frontier, and deputy bans Vladislav Bukovački and Juraj Mindsenti arrived. The castle walls on the east side were partially breached by Ottoman artillery.[21][22]

The town of Cazin was captured on 18 July. By the end of the year, most of the area between the Una and the Glina river was under Ottoman control. The remaining Croatian strongholds in the area were isolated and their surroundings were desolated. The difficult situation in the country was also affected by the unclear position of the banship as both Alapić and Drašković asked the Emperor to relieve them of their duties. The banship was then offered to Krsto Ungnad, but his terms were rejected by the Emperor. On 12 October, Maximilian II died and his son, Rudolf II, succeeded him. Rudolf II sent letters to both Drašković and Alapić, asking them to continue performing their duties. On 25 December, Habsburg and Ottoman representatives signed an 8-year peace treaty.[23][24]

The Croatian line of defense in 1577 stretched from the Drava River to the town of Senj.[23] 4,729 men were stationed in border forts and towns. The Habsburg authorities planned to strengthen the Military Frontier and increase the number of soldiers.[25] Rudolf II gave the task of strengthening the frontier to his uncle, Charles II.[22]

Another wave of Ottoman raids began in July around Bihać and in the Kordun region. In September, Ferhad Pasha Sokolović personally led an army that captured the remaining forts up to the Glina River, north of Cazin.[26]

Ruins of the Gvozdansko Castle in 2013

In early October, a large Ottoman army was led by Ferhad Pasha and Kapidži-pasha into central Croatia.[27] On 3 October, these forces besieged Gvozdansko.[26] The fort was defended by around 300 men, mostly miners and soldiers, under the command of four experienced captains: Damjan Doktorović, Jure Gvozdanović, Nikola Ožegović, and Andrija Stepšić.[17] One soldier managed to pass through Ottoman lines and reach the Croatian-held town of Steničnjak. However, the lack of soldiers prevented a counterattack. It was also expected that Gvozdansko would be able to withstand the siege until winter, when the Ottoman withdrawal was predicted. Ferhad Pasha deployed the artilley on surrounding hills and ordered a prolonged bombardment of the fort.[28] The siege prevented the supply of food and ammunition to the fort. There was also a lack of water.[23] The last supplies to the fort were brought in August. A part of the Ottoman army was left to keep Gvozdansko under siege, while Ferhad Pasha led the rest and attacked the remaining neighboring forts, including Ostrožac that was captured on 13 November. After a short siege, the Zrin Castle, formerly the seat of the Zrinski family, was captured on 20 December. The fall of Zrin left Gvozdansko completely surrounded by Ottoman held forts and towns.[29]

The main part of the Ottoman army joined the besieging force near Gvozdansko at the end of December. Around 5,000 troops with 30 cannons encamped around Gvozdansko, and about the same number of troops was positioned in its vicinity.[17] The fort was already under siege for more than 2 months. The defending force lacked food and ammunition and suffered from hunger, thirst, and cold, while many died or were wounded in combat.[30] All calls for surrender were rejected. Three major assaults on Gvozdansko were repelled on 10, 11, and 12 January, leaving only around 30 men still alive that held their positions on the last days of the siege.[29]

The final assault was planned for the night of 12–13 January, but around midnight the lights in the fort went out. The commanders thought it was a trap and the attack was postponed for the morning. When the Ottomans breached the castle gates at dawn, they met no resistance and found corpses of soldiers wounded and frozen to death. Ferhad Pasha Sokolović ordered a Christian burial for the dead with military honors.[31][30]

The loss of Gvozdansko and other strongholds, including Ostrožac, Cazin, Bužim, and Zrin, led to many changes in the organization of the defence. On 6 February 1578, Krsto Ungnad was confirmed as the new Ban of Croatia by the Croatian Parliament. The administration of the Croatian Military Frontier was entrusted to Archduke Charles II on 25 February.[32] Rudolf's brother, Ernest, was placed in command of the Military Frontier between the Drava River and Transylvania.[33] Charles II was given the right to summon a War Council in Graz and appoint generals, captains, and other officers in the frontier. The Croatian ban was subordinated to the archduke in military affairs.[32] Inner Austrian duchies provided financial support for the Military Frontier and were given seats on the Graz War Council, which was independent of the Vienna War Council (German: Hofkriegsrat). The former civil administration of the frontier was replaced with Habsburg military officials. Such an organization further separated the frontier from Croatian authorities.[34]

Following the capture of Gvozdansko, all nearby mines were destroyed.[31] The Ottomans placed a permanent garrison in the fort in December 1578. Its walls were rebuilt in 1579 and the fort was equipped with additional cannons. Gvozdansko remained under Ottoman control until 1685.[35] However, Ottomans recaptured it in 1690 and held until 1718.[36]

• Pavičić, Ante Tresić (2000). Gvozdansko: epos u 32 pjevanja (in Croatian). AGM. ISBN 9789531741064.